The manufacture of an integrated circuit device requires the formation of various materials onto a base substrate to form necessary circuit structures. During the manufacturing process, chemical-mechanical polishing (CMP) is employed to remove certain layers or reduce a layer to a precise thickness. More specifically, CMP employs the combination of chemical etching and mechanical abrasion to remove excess material. In the case of dielectric films, CMP is typically employed to planarize the surface. For metal films, such as copper, CMP is typically used to remove excess material so as to permit the delineation of electrically isolated circuit interconnects. Also, it might be assumed that semiconductor manufacturing processes produce precisely uniform layers of conductive, semiconductive and non-conductive materials. As with any physical process, however, there are imperfections in the processes that can contribute to non-planarity of the wafer.
FIG. 1 illustrates a portion of a typical CMP tool 100. The CMP tool 100 includes a platen 110 coupled to a spindle 120. The platen 110 may be capable of movement relative to a wafer carrier 160 and a wafer 170. The platen may rotate about the spindle 120 or other axes, translate in a plane, or orbit about an axis. Multiple variations of these types of movements are well known in the prior art. Coupled to the top of the platen 110 is a polishing pad 130. Within the polishing pad 130 are probe windows 132, 134 for probes 140, 142. The wafer 170 is held in the wafer carrier 160 by a wafer ring 162.
During the CMP process, a slurry 150 is applied to the top of the polishing pad 130 and the wafer 170 in the wafer carrier 160 is simultaneously moved (translated, rotated and/or orbited) relative to the platen 110 and pressed against the polishing pad 130 and the slurry 150. The action of the pressure and relative motion of the wafer carrier 160 and/or the platen 110 causes the removal and planarization of the material (also called film layers) that cover the wafer 170. The CMP process, however, may remove material faster from one portion of the wafer versus another portion of the wafer. For example, the CMP process may remove more material from the annular portion of the edge of the wafer than from the center of the wafer. This inconsistency is based upon the slurry 150, temperature, the material on the wafer, the amount of pressure, the movement of the wafer carrier 160 and the platen 110, and other factors.
To help control the inconsistencies of the CMP process, it is desirable to monitor the characteristics of the film layers so that the removal process is controlled and stopped appropriately. Excessive or improper polishing may often result in severely damaged circuit structures on the wafer 170. Some systems employ optical monitoring methods to help prevent excessive or improper polishing. These optical monitoring methods determine a thickness of the film layer by analyzing the optical reflectance spectrum from the film layer. However, in order for such an analysis to be practical, three criteria should be met: (1) the reflection spectrum should be obtained in situ from a wafer in a timely manner without interfering with the CMP process, (2) the quality of the reflection spectrum should be sufficiently good such that the analysis can yield reliable, accurate and relevant information, and (3) practical algorithms should exist with which to do the analysis. Previous optical monitoring systems have failed to meet at least one of the criteria listed above.
Accordingly, what is needed in the art is a system that overcomes the deficiencies of the prior art.
To address the above-discussed deficiencies of the prior art, the present invention provides, for use with a chemical mechanical polishing (CMP) apparatus for polishing a semiconductor wafer, the CMP apparatus having a platen, a polishing pad coupleable with a top surface of the platen and a wafer carrier, an optical closed-loop control system, a method of manufacture and a method of operation thereof. In one embodiment, the optical closed-loop control system includes a plurality of optical probes impacting a corresponding probe window and rigidly mountable through the platen. The probe window is positioned within the polishing pad. The optical closed-loop control system also includes a flash lamp configured to provide light to each of the plurality of optical probes and minimize an exposure time of the light onto the semiconductor wafer, and a spectrograph configured to spatially image light received by each of the plurality of optical probes to a common charge-coupled device (CCD) and produce real-time spectral reflectometry data therefrom. The optical closed-loop control system further includes a control subsystem configured to analyze the real-time spectral reflectometry data and determine at least one wafer state parameter therefrom, and cause the polishing to be adjusted based upon the at least one wafer state parameter. For purposes of the present invention, the phrase “configured to” means that the device, the system or the subsystem includes the necessary software, hardware, firmware or a combination thereof to accomplish the stated task.
In another embodiment, the present invention provides a method of manufacturing an optical closed-loop control system for use with a chemical mechanical polishing (CMP) apparatus for polishing a semiconductor wafer, the CMP apparatus having a platen, a polishing pad coupleable with a top surface of the platen and a wafer carrier, the method includes rigidly mounting through the platen a plurality of optical probes impacting a corresponding probe window, the probe window positioned within the polishing pad. The method also includes coupling a flash lamp to each of the plurality of optical probes to provide light thereto and configuring the flash lamp to minimize an exposure time of the light onto the semiconductor wafer. The method further includes configuring a spectrograph to spatially image light received by each of the plurality of optical probes to a common charge-coupled device (CCD) and producing real-time spectral reflectometry data therefrom. The method still further includes configuring a control subsystem to analyze the real-time spectral reflectometry data and determine at least one wafer state parameter therefrom, and cause the polishing to be adjusted based upon the at least one wafer state parameter.
The present invention also provides, in one embodiment, a method of operating an optical closed-loop control system for use with a chemical mechanical polishing (CMP) apparatus for polishing a semiconductor wafer, the CMP apparatus having a platen, a polishing pad coupleable with a top surface of the platen and a wafer carrier, the method including: (1) employing a plurality of optical probes impacting a corresponding probe window and rigidly mountable through the platen, the probe window positioned within the polishing pad, (2) providing light to each of the plurality of optical probes employing a flash lamp and minimizing an exposure time of the light onto the semiconductor wafer, (3) spatially imaging light received by each of the plurality of optical probes to a common charge-coupled device (CCD) of a spectrograph and producing real-time spectral reflectometry data therefrom, and (4) analyzing the real-time spectral reflectometry data, determining at least one wafer state parameter from the real-time spectral reflectometry data, and causing the polishing to be adjusted based upon the at least one wafer state parameter.
In another embodiment, the present invention also provides an optical closed-loop control system for use with a chemical mechanical polishing (CMP) apparatus for polishing a semiconductor wafer, the CMP apparatus having a platen, a polishing pad coupleable with a top surface of the platen, a plurality of probe windows within the polishing pad and a wafer carrier. The optical closed-loop control system includes: (1) a plurality of optical probes coupleable to corresponding ones of the plurality of probe windows and mountable through the platen, (2) a flash lamp configured to provide light to each of the plurality of optical probes, (3) a spectrograph configured to spatially image light received by each of the plurality of optical probes and produce real-time spectral reflectometry data therefrom, and (4) a control subsystem configured to employ a n-band analysis to analyze the real-time spectral reflectometry data and determine at least one wafer state parameter therefrom, and cause the polishing to be adjusted based upon the at least one wafer state parameter.
In yet another embodiment, the present invention provides an optical closed-loop control system for use with a chemical mechanical polishing (CMP) apparatus for polishing a semiconductor wafer, the CMP apparatus having a platen, a polishing pad coupleable with a top surface of the platen, a plurality of probe windows within the polishing pad and a wafer carrier. The optical closed-loop control system includes: (1) a plurality of optical probes coupleable to corresponding ones of the plurality of probe windows and mountable through the platen, (2) a flash lamp configured to provide light to each of the plurality of optical probes, (3) a spectrograph configured to spatially image light received by each of the plurality of optical probes and produce real-time spectral reflectometry data therefrom, and (4) a control subsystem configured to employ a transform analysis to analyze the real-time spectral reflectometry data and determine at least one wafer state parameter therefrom, and cause the polishing to be adjusted based upon the at least one wafer state parameter.
The present invention may also provide an optical closed-loop control system for use with a chemical mechanical polishing (CMP) apparatus for polishing a semiconductor wafer, the CMP apparatus having a platen, a polishing pad coupleable with a top surface of the platen, a plurality of probe windows within the polishing pad and a wafer carrier, where the optical closed-loop control system includes: (1) a plurality of optical probes coupleable to corresponding ones of the plurality of probe windows and mountable through the platen, (2) a flash lamp configured to provide light to each of the plurality of optical probes, (3) a spectrograph configured to spatially image light received by each of the plurality of optical probes and produce real-time spectral reflectometry data therefrom, and (4) a control subsystem configured to employ a metal breakthrough analysis to analyze the real-time spectral reflectometry data and determine at least one wafer state parameter therefrom, and cause the polishing to be adjusted based upon the at least one wafer state parameter.
The present invention, in another embodiment, may provide an optical closed-loop control system for use with a chemical mechanical polishing (CMP) apparatus for polishing a semiconductor wafer, the CMP apparatus having a platen, a polishing pad coupleable with a top surface of the platen, a plurality of probe windows within the polishing pad and a wafer carrier, where the optical closed-loop control system includes: (1) a plurality of optical probes coupleable to corresponding ones of the plurality of probe windows and mountable through the platen, (2) a flash lamp configured to provide light to each of the plurality of optical probes, (3) a spectrograph configured to spatially image light received by each of the plurality of optical probes and produce real-time spectral reflectometry data therefrom, and (4) a control subsystem configured to employ a model analysis to analyze the real-time spectral reflectometry data and determine at least one wafer state parameter therefrom, and cause the polishing to be adjusted based upon the at least one wafer state parameter.
The foregoing has outlined preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention.